“Tied-truss” sanctuary roof structure (revised from 8/12/23 version)

ROOF DESIGN is an abiding topic of interest to firefighters, because they need to quickly evaluate the stability of burning buildings. Thus it is not surprising that John W. Mittendorf, a retired battalion chief and training commander for the Los Angeles Fire Dept., discussed various types of roof construction in 2004 on the website Fire Engineering. His articles focused on “older truss roofs” — those that were common in large buildings constructed from the 1800s until the 1950s.

Chief Mittendorf, circa 1993

Below the jump, this post discusses what I learned about Mishkon’s sanctuary roof from Chief Mittendorf’s articles.

Sanctuary transverse section drawing (from 2003 Historic Structure Report)
Tie rod is marked in red.
(As usual, click/tap on an image to enlarge it.)

Mishkon’s sanctuary roof matches Chief Mittendorf’s description of a tied truss design. (I didn’t previously know what it was called.) Here I have conflated what he wrote in two articles:

The tied truss is an arch roof constructed with a top arch of heavy timber and a steel tie rod underneath each arch. Most wooden members are “rough-cut” or full-size lumber and use steel plates and bolts for connectors. The tie rods have turnbuckles and ensure that the arches do not push the exterior walls outward. Then 1 x 6-inch sheathing is overlaid as a roof base/covering.